Metabolism flow of carbon and energy

1
Metabolism flow of carbon and energy
Autotrophy C from carbon dioxide
Heterotrophy metabolism of organic C
Energy associated with flow of electrons oxidatio
n/reduction reactions oxidation removal
of e- and H reduction addition of e- and
H two schemes fermentation and respiration
2
Fermentation vs. Respiration fermentation
no oxygen organic compound is final e- and H
acceptor respiration oxygen is the final
e- and H acceptor
3
Fermentation vs. Respiration fermentation
no oxygen organic compound is final e- and H
acceptor respiration oxygen is the final
e- and H acceptor - - - - - - - - - - - - - -
- - - - - - - - - - - - - - - - - - - - - - - - -
- - - - - intermediates in metabolic
scheme NAD and NADP - transitory e- carriers
reoxidation mandatory!
4
Fermentation vs. Respiration fermentation
no oxygen organic compound is final e- and H
acceptor respiration oxygen is the final
e- and H acceptor - - - - - - - - - - - - - -
- - - - - - - - - - - - - - - - - - - - - - - - -
- - - - - intermediates in metabolic
scheme NAD and NADP - transitory e- carriers
reoxidation mandatory! ATP formed in three
ways substrate level phosphorylation (PEP
ADP ? ) photophosphorylation
oxidative phosphorylation
5
Energy transformations must obey the laws of
chemistry and physics Laws of
Thermodynamics 1st Energy can neither be
created nor destroyed energy can be
interchanged, under restrictions energy changes
in calories 1 calorie 1 gm water from
14.5C to 15.5C
6
Energy transformations must obey the laws of
chemistry and physics Laws of
Thermodynamics 1st Energy can neither be
created nor destroyed energy can be
interchanged, under restrictions energy changes
in calories 1 calorie 1 gm water from
14.5C to 15.5C 2nd Chemical processes proceed
in such a direction that the entropy of the
system and the surroundings increases to a
maximum at equilibrium entropy measure of
randomness or disorder
7
Energy transformations must obey the laws of
chemistry and physics Laws of
Thermodynamics 1st Energy can neither be
created nor destroyed energy can be
interchanged, under restrictions energy changes
in calories 1 calorie 1 gm water from
14.5C to 15.5C 2nd Chemical processes proceed
in such a direction that the entropy of the
system and the surroundings increases to a
maximum at equilibrium entropy measure of
randomness or disorder Also need enthalpy
heat content free energy energy in the
bonds standard free energy change energy to do
work ?G
8
Energy ?G -RT log Keq
products/reactants Keq gt 1 ?G is negative
reaction spontaneous, exergonic Keq lt 1 ?G is
positive reaction not spontaneous energy
needed, endergonic Role of ATP ?G for ATP
? ADP Pi -7.3 kcal/mole exergonic
9
Energy Role of enzymes energy of
activation E S ? ES energy
10
Glycolysis yield 2 pyruvate 2 ATP 2 NADH
H
11
Hexose monophosphate or pentose phosphate
pathway yield
12
Entner-Doudoroff pathway yield 2
pyruvate 1 ATP 2 NADH H
13
Phosphoketolase pathway yield from hexose
1 lactic acid, 1 ethanol, 1 CO2, 1ATP
yield from pentose 1 lactic acid, 1 acetate, 2
ATP
14
Reactions of pyruvate
15
Reactions of pyruvate Krebs cycle
or TCA cycle
16
Electron transport and oxidative phosphorylation
- system of e- carriers which accept and
donate e- /or H sequence?? NADH H ?
FP ? CoQ ? b ? c1 ? c ? a
? a3 ? ½O2 link
to ATP synthesis??
17
Electron transport and oxidative phosphorylation
- system of e- carriers which accept and
donate e- /or H sequence?? NADH H ?
FP ? CoQ ? b ? c1 ? c ? a
? a3 ? ½O2 link
to ATP synthesis?? Chemiosmotic Hypothesis role
of chemicals in demonstrating the link
chain inhibitors cyanide, azide,
uncouplers ionophores valinomycin, nigericin
ATPase inhibitors
18
Electron transport and oxidative phosphorylation
- Chemiosmotic Hypothesis correlating
old data with new information a) 3 ATP for each
pair of electrons from NADH H P/O ratio
of 3 b) 2 H for each ATP synthesized
19
Electron transport and oxidative phosphorylation
- system of e- carriers which accept and
donate e- /or H sequence?? NADH
H ? FP ? CoQ ? c1 ? c ? a ? a3 ? ½O2
? b 2H outside cell
? CoQ proposal Q cycle
20
Q cycle H
H _out_________________________
__________________________
e- Q
QH QH2 c1
c
e-
a
b e-

a3 Q QH
QH2
_________________________________________________
______in H e-
H (FP) ½O2
21
Fermentation vs. Respiration fermentative
organisms have no ETS have ATPase and have
membrane potential WHY a membrane
potential? HOW do they generate a
membrane potential?
22
Fermentation vs. Respiration fermentative
organisms have no ETS have ATPase and have
membrane potential WHY a membrane
potential? HOW do they generate a
membrane potential? fermentation ATP
? ?µH
23
Fermentation vs. Respiration fermentative
organisms have no ETS have ATPase and have
membrane potential WHY a membrane
potential? HOW do they generate a
membrane potential? fermentation ATP
? ?µH biosynthesis transport
motility
24
Fermentation vs. Respiration fermentative
organisms have no ETS have ATPase and have
membrane potential WHY a membrane
potential? HOW do they generate a
membrane potential? fermentation respiratio
n ATP ? ?µH biosynthesis
transport motility
25
Classification products acidic to neutral
to CO2 fermentation e- to organics, most from
pyruvate respiration e- to O2
26
Classification products acidic to neutral
to CO2 fermentation e- to organics, most from
pyruvate respiration e- to O2 acid
products homolactic fermentation
Streptococcus, Lactobacillus cheese
production heterolactic fermentation
Lactobacillus cheese production mixed acid
fermentation E. coli acids
Enterobacter aerogenes acetoin, butanediol
27
Classification mixed acid fermentation
E. coli acids
28
Metabolism biosynthesis C metabolism CO2
fixation Autotrophs CO2 ? organic C
Reductive pentose phosphate pathway
(Calvin cycle) Reductive carboxylic
acid pathway Heterotrophs minor CO2
fixation major importance Replenish
TCA cycle intermediates Synthesize
amino acids porphyrins PEP CO2 ?
oxaloacetic acid pyruvate CO2 ATP ?
oxaloacetic acid Synthesize fatty
acids acetyl-CoA CO2 ? malonyl-CoA
acetyl-CoA acetoacetyl-CoA CO2
29
Metabolism biosynthesis N metabolism sources
NH4 NO3 - NO2- N2 incorporated as
NH4 Assimilitory NO3- reduction nitrate
reductase NO3- ? NO2- nitrite reduction ?
NO2- ? NH4
30
Metabolism biosynthesis N metabolism
Nitrogen fixation 6-15 ATP are required due to
high energy of activation two component enzyme
H donating component reductase N
activating component nitrogenase
ferridoxin e- source ATP energy source
Azotobacter aerobic organism high
respiratory rate anaerobic around enzyme
Rhizobium anaerobic organism legume plant uses
O2 nodules are anaerobic
31
Metabolism biosynthesis N metabolism
Assimilation of NH4 1. glutamate dehydrogenase
needs high NH4 a-KG NH4 NADPH H ?
glutamic acid 2. glutamine synthetase
glutamate synthatase low NH4 glutamate
NH4 ATP ? glutamine glutamine a-KG ?
2 glutamate 3. transamination glutamate
a-keto acid ? a-KG amino acid